Nontrapping mercury switch



Dec. 22, 1942 J- H- STM-EY 2,306,285

ANcmfrfmwme MERCURY swmca Filed'July 28, 1941 I IAVIIIIIII /m/fA/ra, JOJfP//H Jr/Mfr, @y um ma@ A Trae/V5 VJ.

Patented ec. 22, 1.942

NETE STATES TENT FECl

2v Claims.

This invention relates to mercury switches of the metallic tubular type wherein a mass of mercury is caused to ow between two partsl of the switch upon suitable rocking thereof to put the switch in a closed circuit condition. In such switches, particularly where suilcient voltage. isv

handled that might cause arcing within the switch upon ilow of the mercury'to an open circuit condition, it is common practice to employ an arc resisting member therein to control and locate the arc in order to prevent deterioration of the metal parts. This member is generally oi a ceramic nature and is commonly termed a breaker. The switch is so arranged that the mercury must flow through this breaker member to form a bridge between two metal parts. The opening through the breaker will vary in accordance with the size of the switch which, of course, varies with the voltage and current to be handled by the switch. Therefore this breaker opening may in many instances be oi that size which might cause air or gases to be trapped to one side thereof when the mercury completely lls the hole by ow therethrough.

A primary object of the invention is to provide a structure which will prevent trapping of air and gases between a mass of mercury tending to ilow toward one of the metal parts of the switch so that a positive flow of the mercury is always occasioned in order to obtain positive contact between the mercury and the metal member of the switch without any variation throughout a great number of operations of the switch. It is obvious that should any trapping tendency exist, the switch would be quite variable in action since at times the mercury might break through the trapped gases and at other times would not. A switch to be of any value must be certain to operate on each and every operation without failure.

A further important object of the invention is to provide such a. non-trapping structure in a very simple structure that may be produced commercially at a relatively low cost and at the same time will be durable and reliable in operation throughout the life of the switch.

Other objects and advantages of the invention will become apparent to those versed in the art in the following description of one particular form of the invention as illustrated in the accompanying drawing, in which Fig. 1 is a view in side elevation of a switch embodying the invention;

Fig. 2, a view in central longitudinal section through the switch;

Fig. 3, a similar view in section showing a modified form of structure; and

Fig. 4, a view in diametrical section on the line 4 4 in Fig". 2'.

Like characters of reference indicate like parts throughout the several views. in the drawing.

In the form of the switch herein Yshownto which the invention is applied, a body lil is formed out of metal to have a tubular bore Il entering therein from one end. An' insulating sleeve I2, cylindrical in section, is telescoped over the open end of the body 'It to)y have an end of. the sleeve come into abutmentr with a shoulder! I3 provided around the body. The insulating sleeve l2 is made out of any suitable resilient material and is made to have an external diameter which will receive thereover a metal cap It with a forced t so as to provide not only means for frictionally retaining the cap in position relative to the body I 0 but also to provide a gas seal between the two metal members. The cap ifi is proportioned in length relative to the length of the sleeve I2 so that the inner rim of the cap terminates a distance from the shoulder ifi so as to have a dielectric gap therebetween. A ceramic breaker l 5 is herein shown as an annulus held in abutment against the end of the body It] within the sleeve l2, being frictionally gripped by the sleeve I2.

In the form shown in Fig. 2, a metal disc It is held compressibly against the outer face oi the breaker I5 by the end wall of the cap it. EX- tending inwardly and axially of the breaker is a post l1 xed by its outer end to the disc i@ by any suitable means, such as by welding. This post is herein shown as terminating substantially vat the inner face plane of the breaker I5 or a trifle inwardly thereof, that is, toward the body side. The breaker i5, as above suggested, may have the hole therethrough vary in size. In the present showing, this hole reduces in diameter from substantially that of the bore il in the body I0 to a smaller diameter at the outer face abutting the disc I6. In any event, regardless oi the size of the hole, it is essential that the hole be tapered from a larger diameter adjacent the body to a smaller diameter at its outer side. The hole through the breaker will be such at times that the major diameter will be less than that of the bore Il.

A mass of mercury i8 is provided within the bore Il to be considerably less than the volume thereof but in such quantity as will interconnect between the inner wall of the bore I I and the disc I6 to give ample electrical contact to carry the required loadwithout undue heating.

By use of the breaker I5 with the tapered bore therein arranged as above described, and by reason ofthe post I1 projecting therein, mercury I8 owing into the breaker bore upon lowering of the cap end of the switch cannot trap air in that bore ahead of the advancing face of the mercury since the mercury will flow around the under side of the post I1 first and air being displaced by the mercury will be pushed upwardly within the hole in the breaker I5 to strike the flared wall thereof and escape back into the bore II to permit the mercury to come into contact with the inner face of the disc I6.

As indicated in Fig. 3, the post I'I may be secured directly to the inner face of the end wall of the cap I4 if desired to eliminate the disc I6 although the use of the disc I6 facilitates production. Otherwise the structure as shown in Fig. 3 is identical to that as shown in Fig. 2. It is evident that the structures shown in Figs. 2 and 3 will in either case provide the full area of mercury contact with the cap I4 or the inter vening disc I6 which in effect is a part of the cap I4. The intrusion of the post II into the mercury entering the breaker I5 will, of course, tend to aid in breaking down the surface or skin resistance of the mercury.

While the invention has herein been shown and described in one particular form, it is obvious that structural changes may be employed without departing from the spirit of the invention and I therefore do not desire to be limited to that precise form beyond the limitations as may be imposed by the following claims.

I claim:

1. A mercury switch having a metallic body with an axial cylindrical bore therein closed at one end and open at the other; a ceramic breaker abutting said body at the open end of said bore,

the breaker having a conically tapered bore therethrough axially aligned with said body bore with the larger diameter ceramic bore end at the body end; a conducting member positioned across and in substantial alignment with said breaker at its smaller diameter end to form a closure thereacross; a cylindrical conducting post fixed to said closure member and axially extending into said breaker bore to terminate therein by a free end substantially at the plane of abutment between said breaker and said body; and a quantity of mercury conned within the body and breaker suflicient to interconnect said post and said body upon the switch being turned to have said conducting member lowermost.

2. A mercury switch having a metallic body with an axial cylindrical bore therein closed at one end and open at the other; a ceramic breaker abutting said body at the open end of said bore, the breaker having a conically tapered bore therethrough axially aligned with said body bore With the larger diameter ceramic bore end at the body end; a conducting member positioned across and in substantial alignment with said breaker at its smaller diameter end to form a closure thereacross; a cylindrical conducting post xed to said closure member and axially extending into said breaker bore to terminate therein by a free end substantially at the plane of abutment between said breaker and said body; and a quantity of mercury conned within the body and breaker suilcient to interconnect said post and said body upon the switch being turned to have said conducting member lowermost; said conducting member comprising a metallic disc; and a metallic cap extending over said breaker and insulatedly telescoping over said body and com- `pressibly retaining said disc in abutment with said breaker.

JOSEPH H. STALEY. 

